The present invention pertains to an oscillating table, in particular for use in a continuous casting machine, comprising a movable part, coupled via an eccentric to a driving mechanism for introducing an upward and downward oscillation motion.
In a continuous casting machine, used i.a. in steel production, the oscillation table is used to impart to the casting mould an upward and downward oscillation motion, either according to a defined radius or, less frequently, along a vertical direction in order to prevent the cast steel from remaining stuck to the water-cooled copper wall of the mould.
In the presently in use oscillating tables, the applied oscillation frequency is dependent upon the casting speed. The amplitude is fixed but is generally adaptable by exchanging eccentrics.
In the upward motion of the casting mould, there is always a relative speed difference between slab, billet or bloom being formed and the casting mould.
In the downward motion of the casting mould, the speed of the casting mould is initially less than, subsequently equal and thereafter greater than, the speed of the slab, billet or bloom. Upon the end of the descending motion, the speed of the casting mould is again equal to and thereafter less than the speed of the slab.
The period during which the speed of the casting mould in the downward motion is greater than the speed of the billet is referred to as the "negative strip".
The usual driving mechanisms for oscillating tables use linear electric motors driving eccentric shafts via reduction gearboxes and driving shafts. This results in a sinusoidal movement which is not satisfactory because the time during which the speed of the slab is nearly equal to the speed of the mould during the downward movement of the mould and causes the cast steel to stuck to the wall of the mould is too long.